Checkout page error

Hi, I am new to woocommerce, i am facing PHP Fatal error: Class ‘MyException’ not found in /home/httpd/htdocs/wordpress-3.5.1_2.0.1/wp-content/plugins/woocommerce/classes/class-wc-checkout.php on line 662.

I am using WordPress 3.5.1 + woocommerce 2.0.1

Thank for any help.

http://wordpress.org/extend/plugins/woocommerce/